判断字段是否存在于JSON中并且这个字段是JSONArray

  • 记录下实际开发过程中遇到的问题。报错信息:java.lang.ClassCastException: java.lang.String cannot be cast to com.alibaba.fastjson.JSONArray
    模拟调用返回的数据JSON
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    [
        {
            "code": 200,
            "msg": null,
            "data": {
                "basicForm": [
                    {
                        "formType": "1",
                        "formVersion": "73",
                        "emptyJson": {
                            "contactMobile": "",
                            "address": "",
                            "contactCode": "",
                            "contactName": "",
                            "applyerName": "",
                            "contactType": "",
                            "applyerAreaCode": "",
                            "applyerMobile": "",
                            "applyerPageType": "",
                            "applyerPageCode": ""
                        }
                    }
                ],
                "clutterForm": ""
            }
        },
        {
            "code": 200,
            "msg": null,
            "data": {
                "basicForm": [
                    {
                        "formType": "1",
                        "formVersion": "73",
                        "emptyJson": {
                            "contactMobile": "",
                            "address": "",
                            "contactCode": "",
                            "contactName": "",
                            "applyerName": "",
                            "contactType": "",
                            "applyerAreaCode": "",
                            "applyerMobile": "",
                            "applyerPageType": "",
                            "applyerPageCode": ""
                        }
                    }
                ],
                "clutterForm": [
                    {
                        "formVersion": "2",
                        "templateId": "960b1dbd-0acc-4626-8a55-15ff0f1962b3",
                        "pcJson": {
                            "submitBtn": false,
                            "emptyText": "清空",
                            "column": [
                                {
                                    "arrow": false,
                                    "display": true,
                                    "labelWidth": "0px",
                                    "type": "title",
                                    "children": {
                                        "column": []
                                    },
                                    "prop": "yhzsx",
                                    "styles": {
                                        "color": "#000",
                                        "fontSize": "18px"
                                    },
                                    "value": "原核准事项",
                                    "collapse": true
                                },
                                {
                                    "arrow": false,
                                    "display": true,
                                    "labelWidth": "0px",
                                    "type": "title",
                                    "children": {
                                        "column": []
                                    },
                                    "prop": "bghdsx",
                                    "styles": {
                                        "color": "#000",
                                        "fontSize": "18px"
                                    },
                                    "value": "变更后的事项",
                                    "collapse": true
                                }
                            ]
                        },
                        "taskHandleItemCode": "11230000MB1846112W200011606000401"
                    }
                ]
            }
        }
    ]

需求是取出JSON中的”formVersion”的值，这俩条JSON中第一条没有formVersion，而且clutterForm返回的是””,所以要对clutterForm进行校验，实例如下：
注意：在if判断中必须要加上 jsonObject.getJSONObject(data).get(clutterForm) instanceof JSONArray 校验clutterForm是否是一个JSONArray否则会报错

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/**
 * 取出JSON中的"formVersion"的值
 */
public static void main(String[] args) {
 String json1 = "{\"code\":200,\"msg\":null,\"data\":{\"basicForm\":[{\"formType\":\"1\",\"formVersion\":\"73\",\"emptyJson\":{\"contactMobile\":\"\",\"address\":\"\",\"contactCode\":\"\",\"contactName\":\"\",\"applyerName\":\"\",\"contactType\":\"\",\"applyerAreaCode\":\"\",\"applyerMobile\":\"\",\"applyerPageType\":\"\",\"applyerPageCode\":\"\"}}],\"clutterForm\":\"\"}}";
 String json2 = "{\"code\":200,\"msg\":null,\"data\":{\"basicForm\":[{\"formType\":\"1\",\"formVersion\":\"73\",\"emptyJson\":{\"contactMobile\":\"\",\"address\":\"\",\"contactCode\":\"\",\"contactName\":\"\",\"applyerName\":\"\",\"contactType\":\"\",\"applyerAreaCode\":\"\",\"applyerMobile\":\"\",\"applyerPageType\":\"\",\"applyerPageCode\":\"\"}}],\"clutterForm\":[{\"formVersion\":\"2\",\"templateId\":\"960b1dbd-0acc-4626-8a55-15ff0f1962b3\",\"pcJson\":{\"submitBtn\":false,\"emptyText\":\"清空\",\"column\":[{\"arrow\":false,\"display\":true,\"labelWidth\":\"0px\",\"type\":\"title\",\"children\":{\"column\":[]},\"prop\":\"yhzsx\",\"styles\":{\"color\":\"#000\",\"fontSize\":\"18px\"},\"value\":\"原核准事项\",\"collapse\":true},{\"arrow\":false,\"display\":true,\"labelWidth\":\"0px\",\"type\":\"title\",\"children\":{\"column\":[]},\"prop\":\"bghdsx\",\"styles\":{\"color\":\"#000\",\"fontSize\":\"18px\"},\"value\":\"变更后的事项\",\"collapse\":true}]},\"taskHandleItemCode\":\"11230000MB1846112W200011606000401\"}]}}";
 List<String> resultList = new ArrayList<>();
 resultList.add(json1);
 resultList.add(json2);
 JSONObject jsonObject = null;
 int count = 1;
 for (String s : resultList) {
     jsonObject = JSON.parseObject(s);
     String formVersion = "";
     if (jsonObject.containsKey("data")
             && jsonObject.getJSONObject("data").containsKey("clutterForm")
             && jsonObject.getJSONObject("data").get("clutterForm") instanceof JSONArray) {
         JSONArray clutterForm = jsonObject.getJSONObject("data").getJSONArray("clutterForm");
         if (clutterForm != null && clutterForm.size() > 0) {
             JSONObject formObject = clutterForm.getJSONObject(0);
             formVersion = formObject.getString("formVersion");
         } else {
             formVersion = "";
         }
     }
     System.out.println("第" + count + "次version的值：" + formVersion);
     count++;
 }
}

打印结果：

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第1次version的值：
第2次version的值：2

Process finished with exit code 0